For mechanical devices, like loudspeakers, there is foundation for the idea. As the driver plays, the spider & surround tend to "loosen up". This increases compliance, Cms, which decreases Fs. So ... slightly improved bass response after break-in? It's feasible.

For mechanical devices, like loudspeakers, there is foundation for the idea. As the driver plays, the spider & surround tend to "loosen up". This increases compliance, Cms, which decreases Fs. So ... slightly improved bass response after break-in? It's feasible.

Any blinded experimentation that has shown audible differences pre and post "break in" that's compelling? To you knowledge?

And does Fs change with VC temp? Say you got a new pair of midbasses and measure the Fs off the bat...then an hour later after heavy play. Could this lend to the perceived break in phenomenon or is it way too short of a time period?

The seas neos I had did better with some break in, this consisted of attaching a power supply to the car, HAMMERING social distortion on repeat while I took a dip in the pool with the garage door shut. After that they had some high end but they still sucked.

The Vifa XT25's did best after break-in, and a LIGHT one at that, a couple days of commute driving at moderate listening levels opened them up. The vifas I bought from Bang, no difference, the Morels, no difference. Any cone driver... no difference.

When I tested this with a woofer tester earlier this year, the results were minimal at best.
I just searched through my photos and can't find the saved data.
The test was performed under the same conditions, about a week apart. I left the mids running on pink noise for about 12hrs/day. I took a before and after.
The fs shifted only about 1hz and the qts changed only 1/100th. IIRC, the fs actually increased. So, does that tell me anything? Only that I wouldn't dare call it conclusive enough to come to a forum and tell people that mechanical break in is real based on that alone. I'd have to do many tests of the same nature and see what kind of changes occur. Is a 1/100th change in qts enough to consider it 'break in'? I wouldn't think so, but without correlating that with hearing tests, I have no idea.
From a mechanics pov (and maybe the more mechanically accustomed engineers here can delve into this topic further as my kinematics experience is pretty minimal), I wouldn't expect a well built product's parts to change drastically enough to warrant major (listener/tester defined) changes, speaking from purely mass damper standpoint. Hysteresis damping? Again, I'm not about to try to tackle this topic.

I've personally never felt that there was audible differences due to break in. I'm not saying it's not real, but I've just never been able to successfully test for it. Given that hearing memory is hard, unless I were to have done an A/B there's no way for me to say in confidence that a driver sounded better due to break in rather than something else (ie: my becoming accustomed to it).
The best real world test I could think for this would be to find 2 well matched drivers, break in one for x hours, then start A/B'ing the two against each other.

John, if the qts shifts, the fs has to as well since the qts is defined at resonance (fs), irrc.

Any blinded experimentation that has shown audible differences pre and post "break in" that's compelling? To you knowledge?

And does Fs change with VC temp? Say you got a new pair of midbasses and measure the Fs off the bat...then an hour later after heavy play. Could this lend to the perceived break in phenomenon or is it way too short of a time period?

Fs is inversely proportional to the square root of the product of the two energy storage elements (this is true for any second-order system ... electrical, mechanical or acoustic). In the case of an electronic circuit, the two energy storage elements are inductance and capacitance. But in the case of a loudspeaker, the two energy storage elements are mass and compliance :

Fs = 1/[2pi*sqrt(Mms*Cms)]

It's pretty simple, actually

Certainly, we can agree that mass doesn't depend on temperature (well ... depending on who's in the audience, i suppose LOL). But there might be temp dependence in compliance.

I'm inclined to believe there is the potential for some change during the first moments of driver usage as the suspension moves through it's usable range for the first few times. I'd be willing to bet the rate of change falls quickly. That might be why it's hard to hear a difference between the first test and a subsequent test. The initial listening test may already be showing the effects of "break in" if the test lasts any substantial amount of time (relative to the time for a measurement sweep).

So, while there may be a break-in effect, I doubt it manifests itself as major audible differences in most cases. Big changes due to "break-in" would cause me to be suspicious of the materials and construction of the driver. When a manufacturer says something like "just wait until they are broken in" what it really means is "wait until your brain has adapted to the driver". My additional interpretation is "we used materials that are unstable and highly variable over time", which might be a stretch but is where my brain leads me.

For comparison testing across multiple drivers it makes sense to subject each unit to the same "break-in" regimen. Even if there isn't any measurable effect in most cases it's good protocol to do it "just in case" and to get one step ahead of any "well they need break-in" claims.

You don't use science to show that you're right, you use science to become right. - R.Munroe

The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them. - W.L.Bragg

I remember reading Richard Pierce's take on this in one of the audio newsgroups. He made some measurements on hundreds of drivers and found that, generally, they exhibited "break-in" characteristics similar to what others have observed. Then, he put them away and tested them another day and they exhibited the same characteristics. His stance was that they don't "break in" once. They "break in" every time you use them. And only minimally at that.

Good addition. His data for mechanical break-in lines up with many of the mechanisms discussed here. It refutes my thought about it all happening very quickly as his data shows tens of hours being required. Nice to see Dan Wiggins' response in there as well.

He did make a logical mistake around his "listener adaptation" argument. Adaptation doesn't make a bad speaker sound good. It makes it sound slightly less bad. That means it could still be fatiguing over time.

You don't use science to show that you're right, you use science to become right. - R.Munroe

The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them. - W.L.Bragg